For decades, data from a satellite that measured the height of the Earth's seas suggested that
their levels
were unchanging or even decreasing, despite tide gauges around the world showing otherwise. The error in the satellite data hid an alarming truth: The rate of sea level rise has been increasing each year,
Scientific American
reported last week.

Scientists now blame a calibration error in the satellite radar used to measure sea surface height. A new analysis of the data indicates that sea levels have risen, from a rate of 1.8 millimeters per year in 1993 to the current 3.9 millimeters per year.

Oceanographer John Church was one of the first scientists to identify the problem in the satellite's data, in 2015. He told the Scientific American that the correction, which aligns more closely with the tide gauges, is an indication that scientists understand the problem and policymakers must work toward a solution.